The present invention relates to a method for detecting the presence of antibodies in an aqueous sample, which antibodies are specifically directed to an antigen.
Several different methods are previously known for the detection of and quantitation of specific antibodies in biological samples. In one of these methods antigen-coated surfaces of glass, polymer, metal or similar materials are used. Samples possibly containing antibodies specifically directed to the antigen on the surface are applied to the surface, after which the formation of the antibody-antigen complex may be detected in different ways. Thus radioactively labelled antibodies added to the sample may compete with the antibodies in the sample and then the radioactivity specifically bound to the antigen surface is measured. The drawback with such techniques is i.a. the waste of time, the need of expensive and complicated equipment and also the risks of health when using radioactive substances.
It has also been suggested (Adams et al., Journal of Immunological Methods 3 (1973), p. 227-232) to detect the antibody-antigen complexes (1) by observing the increase of wettability upon exposure of the surface to water vapour (2) by staining with a protein dye (e.g. Coomassie Brilliant Blue R) and (3) by observing the interference colour changes on special reflecting surfaces. One common drawback with these methods is the fact that they may give unspecific reactions, as false positive reactions cannot be prevented when samples with a high protein concentration, e.g. undiluted sera, are applied. Besides, no analysis is possible of reacting specific antibodies with respect to their belonging to immunoglobulin classes, which is of a very great interest when diagnosing i.a. infection diseases.